Acrylic based composite fiber and method for production thereof, and fiber composite using the same

ABSTRACT

An object of this invention is to provide an acrylonitrile based composite fiber having a new feeling different from that of an ordinary cellulose acetate fiber, cellulose fiber and acrylic fiber, excellent spinability, fiber properties and process ability of yarn spinning, and excellent functions, in particular, a deodorizing function and a moisture absorbing and retaining property. 
     The composite fiber is comprised of 10 to 40% by weight of cellulose acetate and/or cellulose and 60 to 90% by weight of an acrylonitrile based polymer, and has a structure with the cellulose acetate and/or cellulose forming an island component in a cross section perpendicular to a fiber axis and the acrylonitrile based polymer forming a sea component. Preferably, the cellulose acetate and/or cellulose as the island component communicate with another island component in the fiber axis direction, a vacant hole is provided inside the fiber, or a ratio of the longest diameter and the shortest diameter of the fiber cross section is 2 or less, and 5 or more recess parts of 0.3 μm or more and 3 μm or less width and 0.3 μm or more and 3 μm or less depth are provided in a fiber cross section outer circumferential part. Further preferably, by applying a heat treatment under alkali in a production stage, the moisture absorbing and retaining property can be improved.

TECHNICAL FIELD

This invention relates to an acrylic based composite fiber comprisingcellulose acetate and/or cellulose, and an acrylonitrile based polymer,a method for producing the same, and a fiber composite using the sameand another fiber, such as a knitted woven fabric and a non-wovenfabric.

BACKGROUND ART

An acrylic fiber having an excellent color developing property,bulkiness, heat retaining property and soft feeling is a material usedwidely in a clothes field, accessory field, interior field, materialfield or the like, and it is developed mainly by staple. In contrast,cellulose acetate having an excellent glossiness, color developingproperty and dry feeling is regarded as a high quality clothes material,and it is developed mainly by tow and filament. However, since it doesnot have a fiber physical property durable for yarn spinning, it is notdeveloped by staple.

Recently, development of a new material having a new feeling andfunctions, such as one having a deodorizing function and a moistureabsorbing and retaining function in particular, is highly demanded, andas a method for developing techniques, there is polymer compositing.Complexing of a polymer is an effective method for reciprocatingmaterial characteristics of each other. Several reports have beenprovided on the polymer compositing technique of cellulose acetate andan acrylonitrile based polymer. As to the feeling, for example, atechnique for compositing cellulose acetate and an acrylonitrile basedpolymer is disclosed in Japanese Patent Application Laid-Open (JP-A)Nos. 2-154713, and 3-234808. JP-A No. 2-154713 is for one having afeeling inherent to a conventional acetate fiber, and JP-A No. 3-234808is for one having a feeling inherent to a conventional dry acrylic basedfiber.

As to the deodorizing function, for example, JP-A No. 1-259867 disclosesa technique for orienting a metal ion to an amide oximated fiber.However, according to the technique, since the fiber is colored by a hueinherent to the metal, a ;problem is involved in that an end use islimited. Furthermore, a technique for adding a silicate metal salt or anaminomo silicate metal salt to an acrylic based copolymer (JP-A Nos.9-176917 and 9-291416) has been proposed. Since the technique requires acopolymer having acrylonitrile as a principal constituent unit and a noncompatible polymer having miscibility in addition to an additive, aproduction process is complicated. Additionally, although a techniquefor containing a titanium oxide having a photo catalyst function in afiber (JP-A No. 10-8327) has been proposed, it does not functioneffectively at a place whereat ultraviolet rays are weak.

Moreover, as to the moisture absorbing function, which is often appliedby a post-process, washing resistance is poor. Therefore, a binder suchas acrylic resin, an urethane resin and an epoxy resin is needed forimproving durability, which deteriorates the feeling of the fiberitself, and thus it is problematic. Furthermore, a technique forcompositing a moisture absorbing and discharging component in asynthetic fiber has been proposed. Although the technique (JP-A No.11-279842) has both a moisture absorbing function and a moisturedischarging function, no description is disclosed for a moistureretaining function thereof.

In order to solve the above-mentioned conventional problems, an objectof the invention is to provide an acrylic based composite fiber having anew feeling different from that of a conventional cellulose acetatefiber, cellulose fiber and acrylic fiber, excellent fiber physicalproperties and process ability of yarn spinning, and excellent functionproperties, in particular, a deodorizing function and moisture absorbingand retaining function.

DISCLOSURE OF THE INVENTION

As a result of elaborate discussions by inventors of this invention forsolving the above-mentioned problems, the following invention has beenattained. The object of the invention is an acrylic based compositefiber composed of 10 to 40% by weight of cellulose acetate and/orcellulose and 60 to 90% by weight of an acrylonitrile based polymer,characterized by comprising a structure with the cellulose acetateand/or cellulose forming an island component in a cross sectionperpendicular to a fiber axis (fiber lateral cross section), and theacrylonitrile based polymer forming an sea component, a method forproducing the same, and a fiber composite using the above-mentionedcomposite fiber.

As mentioned above, as a method for developing a new material having anew feeling, compositing of a polymer is effective. The inventorssurprisingly found out, while promoting discussions for a polymercompositing technique concerning the cellulose acetate and/or celluloseand an acrylonitrile based polymer, that the cellulose acetate and/orcellulose have/has a high deodorizing function with respect to acarboxylic acid, in particular to an acetic acid. Accordingly, it wassuggested that by using the cellulose acetate and/or the cellulose as aconstituent component of a fiber product, the deodorizing function canbe realized by an ability of a fiber substrate itself without using acommon deodorizing agent.

Furthermore, it was confirmed that an excellent moisture absorbing andretaining property, which was not provided in conventional acrylic basedsynthetic fibers, was obtained by using the cellulose acetate and/orcellulose and the acrylonitrile based polymer since high standardmoisture regain of a fiber made of the cellulose, such as the celluloseacetate and cotton, could be effectively utilized. Therefore, it wasalso confirmed that by using the cellulose acetate and/or the celluloseas a constituent component of a fiber product, moisture absorbing andretaining performance could be realized by an ability of a fibersubstrate itself without relying on a post process.

In the invention, cellulose diacetate and cellulose triacetate can bepresented as the cellulose acetate. The cellulose diacetate in theinvention has an average acetylation degree of 48.8% or more and lessthan 56.2%, and the cellulose triacetate has an average acetylationdegree of 56.2% or more and less than 62.5%. The cellulose in theinvention may be a polymer containing a cellulose molecular structureC₆H₇O₂(OH)₃, and it may be a cellulose derivative with a chemicalmodification added to a part of a hydroxyl group, such as alkylcellulose, nitro cellulose, cellulose xanthate, and ion exchangecellulose as well.

In the invention, the acrylonitrile based polymer is made ofacrylonitrile and an unsaturated monomer polymerizable therewith. As theunsaturated monomer, an acrylic acid, a methacrylic acid, alkyl estersthereof, vinyl acetate, acrylic amide, vinyl chloride, vinylidenechloride, and furthermore, depending on a purpose, an ionic unsaturatedmonomer such as sodium vinyl benzene sulfonate, sodium methacrylicsulfonate, sodium allyl sulfonate, sodium acrylic amide methyl propanesulfonate, and sodium parasulfophenol methacrylic ether may be used aswell.

According to the composite fiber of the invention, the cellulose acetateand/or cellulose need to be 10 to 40% by weight, preferably 20 to 30% byweight. In the case where they are less than 10%, a feeling of a fiberbecomes similar to that of the acrylic fiber and a dry feeling is lost.In addition, as to a deodorizing ratio of a deodorizing evaluation to bedescribed later, a carboxylic acid is less than 90% and an acetic acidis less than 95%, and thus a high deodorizing ability cannot beobtained. In the case where they are more than 40%, spinability becomespoor, for example fiber breaks are generated at the time of production,and a fiber property is lowered, so that a process ability of yarnspinning becomes poor. Moreover, a soft feeling derived from the acrylicfiber is lost.

According to the invention, the acrylonitrile based polymer needs to be60 to 90%, preferably 70 to 80% by weight. In the case where it is lessthan 60% by weight, the spinability becomes poor, and the fiber physicalproperty is lowered, so that the spinning process passing propertybecomes poor. Moreover, the soft feeling derived form the acrylic fiberis lost. In the case where it is more than 90% by weight, a feeling of afiber to be obtained becomes similar to the feeling of the acrylic fiberso that the dry feeling is lost.

According to the invention, it is important that, in a fiber crosssection, the cellulose acetate and/or cellulose form an islandcomponent, and the acrylonitrile based polymer forms a sea component forobtaining the fiber physical property defined in the invention. Byadopting the structure with the cellulose acetate and/or cellulose beingthe island component and the acrylonitrile based polymer being the seacomponent in the fiber cross section, circumference of the celluloseacetate and/or cellulose, which have vulnerable fiber properties, iscovered with the acrylonitrile based polymer, and consequently the fiberis reinforced so as to obtain the fiber physical property equivalent tothe ordinary acrylic fiber. Moreover, in order to obtain the fiberphysical property equivalent to the ordinary acrylic fiber, a smallerisland size is considered to be advantageous, however, as long as thefiber physical property defined in the invention is satisfied, theisland size is not at all limited.

It is preferable that the sea island structure in the cross section inthe direction perpendicular to the fiber axis (fiber lateral crosssection) has the cellulose acetate and/or cellulose as the islandcomponent in the cross section in a fiber axis direction (fiberlongitudinal cross section) communicating with another island componenttotally or partially for improving the deodorizing function.

In the invention, a vacant hole denotes a gap formed inside the fiber. Apart of the vacant hole may be opened to a fiber surface, and moreover,the vacant hole may interlock the islands with each other. A form and asize of the vacant hole are not limited at all. Since it is preferableto maintain a fiber strength at 1.8 CN/dTex or more, those of about lessthan 2 to 5 μm are preferable though it depends on the form of thevacant hole. Furthermore, according to the invention, although a densestructure without a vacant hole inside the fiber is considered to beadvantageous for maintaining the fiber physical property, existence orabsence of the vacant hole is not at all limited as long as the fiberphysical property defined in the invention is satisfied. In the case ofan application for the purpose of retaining temperature and lightweight, it is rather advantageous to provide the vacant hole.

As to the feeling of the fiber to be obtained, by satisfying a ratio ofthe longest diameter and the shortest diameter of the fiber crosssection and a number of recess parts in a fiber cross section outercircumferential part, dry, tense, and soft feelings can be provided,which is different from conventional fibers, for example, celluloseacetate fiber, fibers made of cellulose such as cotton, rayon, cupra, orthe like, and an acrylic fiber. In addition, it is also effective forthe deodorizing.

That is, it is preferable that the ratio of the longest. diameter andthe shortest diameter of the fiber cross section is 2 or less, and 5 ormore recess parts of 0.3 μm or more and 3 μm or less width and 0.3 μm ormore and 3 μm or less depth are provided in the fiber cross sectionouter circumferential part for the new feelings and improving thedeodorizing effect. The longest diameter in the invention is a diameterof a circumscribing circle in contact with the fiber cross section outercircumferential part, and the shortest diameter is a diameter of ainscribed circle in contact with the fiber cross section outercircumferential part. The recess part in the fiber cross section outercircumferential part in the invention is a recess part recognizablevisually with an optical microscope, having width and depth of 0.3 μm ormore, which is the lowest limit of a wavelength area of visible light.

Moreover, the width and the depth of the recess part are 3 μm or less.If the recess part is in this range, since it is much smaller than arain droplet diameter (100 μm to 3,000 μm), and it is much larger thanwater vapor (0.00044 μm) (“Special Functional Fiber” published by CMC,p182, 1983), only the water vapor can pass through the recess part andthe water vapor can easily be diffused to the outside, and thus the dryfeeling tends to be generated. Furthermore, depending on a number ofexisting recess parts, color effect which has not been conventionallyprovided can be expected.

Since the ratio of the longest diameter and the shortest diameter of thefiber cross section is 2 or less, bending rigidity is increased so as toprovide an appropriate tense feeling, and since 5 or more recess partsof 0.3 μm or more and 3 μm or less width and 0.3 μm or more and 3 μm orless depth are provided in the fiber cross section outer circumferentialpart, the dry feeling is generated, and friction resistance between thefibers is reduced, so that the soft feeling can be provided. In the casewhere the ratio of the longest diameter and the shortest diameter of thefiber cross section is more than 2, the tense feeling is lost, and inthe case where the recessed parts of 0.3 μm or more and 3 μm or lesswidth and 0.3 μm or more and 3 μm or less depth are provided in thefiber cross section outer circumferential part are provided by less than5, the dry feeling and the soft feeling tend to be lost.

According to the invention, single fiber strength is 1.8 CN/dTex ormore, dry elongation is 30% or more, knot strength is 1.8 CN/dTex ormore, and knot elongation is 30% or more. Within these ranges, ingeneral, process ability of yarn spinning equivalent to that of ordinaryacrylic fiber can be obtained. In the case where the defined fiberphysical properties are not satisfied, that is, if the single fiberstrength is less than 1.8 CN/dTex, the dry elongation is less than 30%,the knot strength is less than 1.8 CN/dTex, or the knot elongation isless than 30%, the process ability of yarn spinning becomes poor.

The carboxylic acid in the invention, any one having a carbonyl group ina molecule, and capable of being present in the air can be used.Moreover, the carboxylic acid may be any of a monocarboxylic acid, adicarboxylic acid, and polycarboxylic acid, and it may be saturated orunsaturated. Furthermore, a structure having a functional group otherthan the carbonyl group may be used as well. Carboxylic acid species arenot particularly limited as long as the above-mentioned conditions aresatisfied. For example, those having an unpleasant strange odor orstimulus odor in a daily life, such as a formic acid, an acetic acid, apropionic acid, a lactic acid, an isolactic acid, a valeric acid, anisovaleric acid, a capronic acid, a 2-ethyl lactic acid, a capric acid,a 2-ethyl hexanic acid and an oleic acid, can be presented.

As to adsorption performance, it is important that a adsorption ratio ofthe carboxylic acid is 90% or more in the air including 100 ppm or lesscarboxylic acid by a measurement method to be described later.Carboxylic acid concentration in the air is set at 100 ppm as apractical evaluation density based on a daily life. In the case wherethe carboxylic acid adsorption ratio in the air including 100 ppm orless carboxylic acid is less than 90%, the adsorption ability isinsufficient. Furthermore, in the case where the carboxylic acidadsorption ratio in the air including 100 ppm or less carboxylic acid isless than 90%, tolerant concentration of the acetic acid as arepresentative example of the stimulus odor of the carboxylic acidspecies, which is 10 ppm, (Principal Chemical Products 1,000 KindsToxicity Data Special Research Report, p19, Kaigai Gijutsu ShiryoKenkyusho, 1973) cannot be satisfied. According to the invention, sincethe deodorizing ratio with respect to the acetic acid is 95% or more,the tolerance concentration can be satisfied sufficiently. In the casewhere the deodorizing ratio of the acetic acid is less than 90%, anadsorption ability tends to be insufficient.

In the invention, the air including the carboxylic acid is not at alllimited as to inclusion of another gas component species as long as asingle or composite carboxylic acid species is/are provided as a part ofconstituent components in the air, and the carboxylic acid is 100 ppm orless. A mechanism of the excellent deodorizing property of the celluloseacetate and/or cellulose is not clear yet at the present, however, theinventors assume that a hydrophilic group of the cellulose acetateand/or cellulose and an acetyl group of a cellulose acetate side chainare related thereto. That is, a carboxylic group has a hydrophobic partand a hydrophilic part in a molecule, and it is assumed that thehydrophobic part thereof is adsorbed to the acetyl group of thecellulose acetate side chain, and on the other hand, the hydrophilicpart is adsorbed to the cellulose acetate and/or cellulose via anaffinity with a water molecule so as to realize an excellent deodorizingability.

Then, according to the invention, the cellulose acetate and/or cellulosehave/has a particularly high deodorizing ability with respect to theacetic acid. The reason thereof is presumed that the acetyl group in theacetic acid and the acetyl group of the cellulose acetate side chainhave stronger affinities. Since the invention has the deodorizingproperty for a nonenal as an aldehyde compound, with a premise that theabove-mentioned mechanism is correct, it is easily presumed that thesame deodorizing ability can be also realized with respect to asubstance in the air having a hydrophobic part and a hydrophilic part ina molecule. In the case where the deodorizing ratio of the nonanal isless than 90%, the adsorption ability tends to be insufficient.Preferably, the deodorizing ratio is 95% and more According to theinvention, it is important that a moisture absorbing ratio Aa under a40° C. temperature and 90% RH humidity environment is 15.0% or less, anda moisture absorbing ratio Ab under the 20° C. temperature and 65% RHhumidity environment is more than 2% in terms of appropriate supply of amoisture absorbing property. That is, as to the moisture absorbing ratioof the invention, Ab under an average temperature and humidityenvironment is more than 2%, and Aa under a high temperature and highhumidity environment is 15.0% or less equivalent to the standardmoisture regain of wool as a natural fiber ,which is 15%, (“Fiberhandbook 2001”, edited by Nihon Kagaku Senni Kyokai, published inDecember 2000), and thus the moisture absorbing property with littlesticky feeling can be obtained.

Although a desired moisture absorbing property can be obtained byoptionally setting a mixing ratio of the acrylic based composite fiberaccording to the invention in a fiber product to be obtained, preferablythe moisture absorbing ratio Aa is 3.0% or more and 8.0% or less (lessthan 8.5%, which is the standard moisture regain of cotton as arepresentative of a natural fiber). In the case where it is less than3.0%, a sufficient moisture absorbing property tends not to be obtained.Moreover, the moisture absorbing ratio Ab is preferably more than 2.0%and less than 6.5%. In the case where Ab is 2.0% or less, the sufficientmoisture absorbing property tends to be hardly obtained. In the case ofrealizing the moisture absorbing property of 6.5% or more, content ofthe cellulose acetate and/or cellulose needs to be increased, so thatthe physical properties such as the fiber strength tend to be lowered.

According to the invention, it is important that a moisture absorbingratio difference ΔA (=Ab−Aa) at the time of transfer from thetemperature 40% and 90% RH humidity environment to the 20° C. and 65% RHhumidity environment is 1.5 or less in terms of the supply of a moistureretaining property. That is, it is important that the moisture absorbingratio difference ΔA at the time of transfer from the high temperatureand humidity environment to the average temperature and humidityenvironment satisfies 1.5 or less in terms of keeping the moistureretaining property uninfluenced by environment conditions. In the casewhere ΔA is more than 1.5, the moisture retaining property becomes poor.Therefore, since an appropriate moisture absorbing property and amoisture retaining property are provided under the different environmentconditions in the invention, the moisture absorbing and retainingproperties uninfluenced by the environment conditions can be obtained.This means that the moisture retaining property with little stickyfeeling can be obtained stably even in the case of an externalenvironment change in the summer or winter, or a high temperature andhigh humidity environment in clothes immediately after physicalexercises.

Furthermore, surprisingly, depending on a ratio of the cellulose acetateand/or cellulose and the acrylonitrile based polymer, the acrylic basedcomposite fiber of the invention can obtain the moisture absorbing ratioof 3.5% or more, which is the standard moisture regain of a triacetatefiber, or the ratio equivalent to the standard moisture regain of adiacetate fiber, which is 6.5%, and of wool, which is 15.0% (“Fiberhandbook 2001”, edited by Nihon Kagaku Senni Kyokai, published inDecember 2000). This means that in the case where the ratio of thecellulose acetate and/or cellulose and the acrylonitrile based polymeris same, it tends to be higher than the moisture absorbing ratioobtained from a mixture of a fiber of the cellulose acetate and/or thecellulose and a fiber of the acrylonitrile based polymer (for example, acloth using a blended fiber, a knitted or woven product obtained bycross knitting or cross weaving fibers spun independently, or a pileproduct obtained directly by tufting from a sliver without forming aspun yarn, such as a blanket, or the like). Although a mechanism is notclear at the present, it is presumed that an increase of interfacesbetween the cellulose acetate and/or cellulose and the acrylonitrilebased polymer obtained by the sea island structure is related.

A fiber composite using the acrylic based composite fiber of theinvention, such as a woven or knitted product and a non-woven fabric,has a novel feeling, the deodorizing property and the moisture absorbingand retaining property, which have not been provided conventionally andit may be a fiber composite including 20% by weight or more of theacrylic based composite fiber of the invention, preferably 30% or more.Not only being processed in a spun yarn made of only the acrylic basedcomposite fiber of the invention, it may be also mixed with a syntheticfiber or a semi synthetic fiber such as an ordinary acrylic fiber, apolyester fiber, polyamide fiber and rayon short fiber, and/or cotton,ram wool, or the like. Moreover, it may be cross knit or cross wovenwith a long fiber such as the above-mentioned synthetic fiber or thesemi synthetic fiber and silk. In particular, cloth obtained by mixing,cross knitting or cross weaving with rayon or ram wool is provided witha unique feeling, and it is effective in deodorizing not only an aceticacid odor but also an ammonium odor.

The fiber composite such as the woven or knitted product or thenon-woven fabric using the acrylic composite fiber according to theinvention has a novel feeling and moisture absorbing and retainingproperty, which have not been provided conventionally. It may beprovided as a fiber composite including 20% by weight or more of theacrylic based composite fiber of the invention, preferably 30% by weightor more, and further preferably 50% by weight or more in view ofobtainment of a mixing homogeneity. Moreover, the fiber composite usingthe fiber of the invention is not limited to the woven or knittedproduct and the non-woven fabric, and it is needless to say that it canbe also applied to a fiber composite such as a pile.

As end use of the fiber composite using the acrylic based compositefiber of the invention, clothing applications such as a sweater, aninner, a shirt, socks, a jersey, and a skirt, bedding applications suchas a blanket and a sheet, interior applications such as a carpet, a mat,a chair covering and a curtain, miscellaneous applications such astoiletry goods, an artificial fur, and a stuffed animal, and anapplication for handicraft thread, or the like can be presented.

The fiber of the invention can be produced for example as follows.First, an acrylic based composite fiber of the invention comprising thecellulose acetate and the acrylonitrile based polymer is obtained, andnext, an acrylic based composite fiber of the invention comprising thecellulose acetate, the cellulose and the acrylonitrile based polymer isobtained, and furthermore, an acrylic based composite fiber of theinvention comprising the cellulose and the acrylonitrile based polymeris obtained. Hereinafter, it will be explained successively.

A spinning solution made of cellulose acetate, an acrylonitrile basedpolymer and a solvent is prepared. The solvent is not particularlylimited as long as it is a solvent capable of dissolving both thecellulose acetate and the acrylonitrile based polymer. And any of aninorganic acid based one, an inorganic base aqueous solution based one,and an organic solvent can be used. As the solvent, for example, anitric acid (aqueous solution), a zinc chloride aqueous solution, arhodanide aqueous solution, dimethyl formamide, dimethyl acetamide,dimethyl sulfoxide, ethylene carbonate, propylene carbonate,γ-butylolactone, acetone, or the like can be presented.

As to a method for preparing the spinning solution, it may be adjustedby agitating and mixing the cellulose acetate, the acrylonitrile basedpolymer and the solvent at the same time at a room temperature, or byheating or cooling as needed, however, it is also possible to dissolvethe cellulose acetate and the acrylonitrile based polymer independentlyin the solvent and mix them.

In order to obtain the acrylic based composite fiber made of thecellulose acetate and the acrylonitrile based polymer, having a fiberstructure with the cellulose acetate as the island component and theacrylonitrile based polymer as the sea component in the cross section inthe direction perpendicular to the fiber axis according to theinvention, a wet spinning method is used, which provides easycontrollability of a coagulation speed of the spinning solution forforming the recess parts in the fiber cross section outercircumferential part. Since the coagulation speed by a dry jet wetspinning method and a dry spinning method other than the wet spinningmethod is slow, the recess part formation in the fiber cross sectionouter circumferential part becomes difficult.

The spinning solution is made into a coagulated filament using anordinary spinnerette, and it is drawn to 3 to 7 times drawing ratio. Inthe case where the drawing ratio is less than 3 times, mechanicalstrength of the fiber is lowered, so that spinability and productdurability are lowered. In the case where the drawing ratio is more than7 times, process troubles such as+++ a thread break can be easilygenerated. An oiling process and a drying process are applied to a drawnthread by an ordinary method. In this production method of theinvention, functional materials, for example, a fluorine based compoundincluding a pollution preventive substance, an amine based compound ornatural based substances such as a chitin and a chitosan having anantibacterial activity, can be applied to a thread before drying andcollapsing processes (a coagulated thread, a washed thread and a drawnthread).

The composite fiber made of the cellulose acetate and the acrylonitrilebased polymer of the invention accordingly obtained becomes anacrylonitrile based composite fiber with a totally novel feeling, whichhas not been provided in a conventional cellulose acetate fiber, acellulose fiber or an acrylic fiber, and an excellent spinability, fiberphysical property, process ability of the (yarn) spinning, deodorizingproperty and moisture retaining property by having the composite ratio,the ratio of the longest diameter and the shortest diameter in the fibercross section, the size and the number of the recess parts in the fibercross section outer circumferential part each at a desired value bychanging a mixing ratio of the components cellulose acetate (A) andacrylonitrile based polymer (B), a ratio of the longest diameter and theshortest diameter of a spinnerette hole and a coagulation condition inspinning.

Furthermore, by further processing the composite fiber of the celluloseacetate and the acrylonitrile based polymer of the invention obtained asmentioned above by a heating process under alkali, for example, aprocess with a sodium hydroxide of 12% concentration at 60° C. for about30 minutes with a cotton dyeing machine, a cheese dyeing machine, a hankdyeing machine, or the like, the cellulose acetate becomes cellulose, sothat the acrylonitrile based composite fiber made of the celluloseacetate ,the cellulose and the acrylonitrile based polymer of theinvention, having the excellent moisture absorbing property, can beobtained. Moreover, depending on the concentration of the sodiumhydroxide or the processing condition, the acrylonitrile based compositefiber made of the cellulose and the acrylonitrile based polymer of theinvention can be obtained. Although an alkaline agent to be used is notparticularly limited, it is preferable to use a strong alkaline such asthe sodium hydroxide.

Moreover, since the moisture absorbing and retaining performance isimproved by the cellulose process, the mixing ratio of the fiber ofinvention in an end use product can be lowered, and the mixing ratio ofanother functional fiber can be increased. Therefore a productapplication for end use can be widened. Furthermore, it is alsoeffective in terms of widening of the product application for end use toapply a chemical modification to a part of the hydroxyl group after thecellulose process so as to have a cellulose derivative, such as alkylcellulose, nitro cellulose, cellulose xanthane, and ion exchangecellulose.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a set of electron microscope photographs of lateral crosssectional views of each fiber of Examples 1 and 3 according to theinvention and Comparative examples 2 and 4.

FIG. 2 is a set of longitudinal cross sectional views of the same.

FIG. 3 is a graph showing evaluation results of moisture absorbingproperties of fibers of Example 9 and Comparative example 7.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the invention will be explained furtherspecifically based on representative examples.

In the examples below, the phrase “% by weight” is indicated simply as“%”.

(Ratio of the Longest Diameter and the Shortest Diameter in a FiberCross Section and a Number of Recess Parts in a Fiber Cross SectionOuter Circumferential Part)

After wrapping a fiber bundle in a paraffin resin, and cutting to a 5 μmthin layer with a microtome, a cut surface was observed with atransmission type optical microscope (produced by Nikon Corp.,biological microscope E-800), so that a number of the recess parts of0.3 μm or more and 3 μm or less width and 0.3 μm or more and 3 μm orless depth in a fiber cross section outer circumferential part wascounted by visual observation.

(Observation Method for a Sea Island Structure)

After wrapping a fiber bundle in a two-liquid-type urethane resin, andcutting to 2 mm length with a safety razor, an ion plasma etchingprocess was applied to a cut surface with a plasma reactor (produced byYamato Kagaku Corp., PR-302). After applying metal sputtering to aprocessed surface by an ordinary method, it was observed with a scanningtype electron microscope (produced by Nihon Denshi Corp., JSM-T20).

(Single Fiber Strength, Dry Elongation, Knot Strength and KnotElongation)

Methods of 8.7 (tensile strength and a stretching ratio) and 8.8 (knotstrength) of JIS L 1015 were used to test a chemical fiber staple.

(Feeling Evaluation)

Dry, tense and soft feelings were evaluated by a sensory test bytouching with hands.

(Deodorizing Ratio)

As odor components for a deodorizing evaluation, an isovaleric acid andan acetic acid as representative odors of a carboxylic acid, and anonenal (C₆H₁₉O) as an aldehyde compound were selected.

1 g of a specimen left still under a 20° C. temperature and 65% RHhumidity environment for 24 hours was sealed in a 370 mL triangularflask adjusted so as to have a 50 ppm gas concentration of theisovaleric acid or the acetic acid. After leaving for 1 hour, the gasconcentration in the flask was measured with a detector tube (Kitagawatype gas detector). For a comparison, measurement was made in the samemanner except that the specimen was not sealed for obtaining the gasconcentration in the flask after leaving for 1 hour.

A deodorizing ratio was calculated as a ratio of the gas concentrationwith the specimen sealed with respect to the gas concentration of thecomparison.

In the case of an ammonium as the odor component of the deodorizingevaluation, it was evaluated in the same manner except that ammonium gasconcentration was adjusted to 110 ppm in the above-mentioned evaluationmethod.

In the case of the nonenal as the odor component of the deodorizingevaluation, 1 g of a specimen left still under a 20° C. temperature and65% RH humidity environment for 24 hours was sealed in a 125 mL glassBayer bottle adjusted so as to have a 30 ppm gas concentration of thenonenal. After leaving for 2 hours, a nonenal gas concentration wasmeasured with a gas chromatograph. For a comparison, measurement wasmade in the same manner except that the specimen was not sealed forobtaining a relative deodorizing ratio from a peak area of a gaschromatography.

(Moisture Absorbing Ratio)

After leaving 5 g of a specimen under a 40° C. temperature and 90% RHhumidity environment for 24 hours, it was collected for measuring a massand an absolute dry mass thereof. By the following formula, a moistureabsorbing ratio Aa (%) was calculated. In the same manner, a moistureabsorbing ratio Ab of the same evaluation method except that it is undera 20° C. temperature and a 65% humidity environment was also calculatedby the following formula.Moisture absorbing ratio (Aa or Ab)=(mass at the time ofcollection−absolute dry mass)/absolute dry mass×100(Cellulose Acetate Weight Reduction Ratio)

After soaking a specimen in an acetone and applying a heat treatment at70° C. for 20 minutes, it was washed and dried absolutely for measuringits weight. In the case where cellulose acetate is included in thespecimen, since the cellulose acetate is extracted by the acetone, theweight is reduced. However, in the case where the cellulose acetate ischanged into cellulose, weight change does not take place. The weightchange before and after the acetone extracting process was provided as acellulose acetate weight reduction ratio.

Hereinafter, with reference to Examples and Comparative examples of theinvention, characteristics will be compared. “Spinability, feeling anddeodorizing property of Examples 1 to 5 and Comparative examples 1 to 5”

Spinning solutions were obtained by mixing and dissolving a cellulosediacetate (A) having a 55.2% average acetylation degree and anacrylonitrile based polymer (B) (acrylonitrile/vinyl acetate=93/7 byweight ratio) having a 1.98 reduction viscosity of a 0.5% dimethylformamide measurement obtained by aqueous dispersion polymerizationmethod with solid component ratios shown in Table 1 in a dimethylacetamide so as to have a 22% solid component concentration. Thespinning solutions were discharged into a spinning bath consisting of56% dimethylacetamide aqueous solution at 35° C. using a round shapespinarette and drawn to 6 times while washing with boiling water toprepare drawn filaments. After that, the filaments were dried andannealed to prepare fiber with a monofilament fineness of 2.2 dTex.

Evaluation on the fibers with different solid component ratios of(A)/(B) in terms of spinability, existence or absence of a sea islandstructure, a ratio of the longest diameter and the shortest diameter ofa fiber cross section, a number of recess parts of 0.3 μm or more and 3μm or less width and 0.3 μm or more and 3 μm or less depth generated ina fiber cross section outer circumferential part, feeling, and adeodorizing property for a isovaleric acid and an acetic acid, is shownin Table 1. Moreover, a spinnerette with round shape holes was usedexcept a case of Example 4 using a spinnerette with elliptical shapeholes that has a 2.0 ratio of a longer axis and a shorter axis. Thedeodorizing property with respect to a nonenal was evaluated for acomposite fiber obtained in Example 3 (single fiber fineness 2.2 dTex)and an acrylic fiber (single fiber fineness 2.2 dTex). Deodorizingratios were 95% and 38% respectively. Moreover, moisture absorbing andretaining property evaluation for fibers used in Examples 1, 3, 5 andComparative examples 1, 2 is shown in Table 2.

TABLE 1 Ratio of longest (A)/(B) Existence/ diameter Number solidabsence of and of Feeling Deodorizing ratio component sea islandshortest recess Dry Tense Soft Isovaleric Acetic ratio Spinabilitystructure diameter parts feeling feeling feeling acid acid Comparative 0/100 Good Absent 2.0 1 Poor Good Good 54 54 example 1 Comparative 5/95 Good Exist 1.5 4 Poor Good Good 73 74 example 2 Example 1 10/90Good Exist 1.4 5 Slightly Good Good 90 95 good Example 2 15/85 GoodExist 1.4 6 Good Good Good 91 96 Example 3 30/70 Good Exist 1.3 9 GoodGood Good 93 98 Example 4 30/70 Good Exist 2.0 8 Good Good Good 92 97Comparative 30/70 Good Exist 2.5 10  Good Poor Good 92 97 example 3Example 5 40/60 Good Exist 1.2 7 Good Good Good 94 98 Comparative 50/50Poor — — — — — — — — example 4 Comparative 100/0  Good Absent 2.0 5 GoodSlightly Slightly 95 98 example 5 good poor

TABLE 2 (A)/(B) solid Moisture Moisture component absorbing absorbingratio ratio Aa (%) ratio Ab (%) ΔA Comparative  0/100 2.4 1.2 1.2example 1 Comparative  5/95 3.1 1.9 1.2 example 2 Example 1 10/90 4.22.8 1.4 Example 3 30/70 6.3 5.0 1.3 Example 5 40/60 7.7 6.3 1.4

FIGS. 1(a) to 1(d) show a lateral cross section of each fiber obtainedby Example 1 and 3, and Comparative examples 2 and 4 by scanningelectron microscope photographs successively. Moreover, FIGS. 2(a) to2(d) show a vertical cross section of each fiber corresponding to thesame examples by scanning type electron photographs successively. Thesefibers were soaked in an acetone at 70° C. for 30 minutes for extractingcellulose diacetate components in the fibers, and an ion plasma etchingprocess was applied thereto for 90 seconds for executing a metalspattering on processed surfaces thereof.

From these figures, it is understood that a fiber component of thecellulose diacetate (A) and the acrylonitrile based polymer (B)constitute a composite fiber having a sea island structure with theacrylonitrile based polymer (B) providing a sea component and thecellulose diacetate (A) providing an island component, and the cellulosediacetate (A) elongates in a fiber direction, partially communicatingwith another island component. Furthermore, the cellulose diacetate (A)component existing on a surface is extracted into the spinning bath, andit forms recess parts in the fiber surface according to a difference ofcoagulation speed between the cellulose diacetate (A) and theacrylonitrile based polymer (B).

Therefore, by changing the solid component ratio (A)/(B) of thecellulose diacetate (A) and the acrylonitrile based polymer (B), avolume of the cellulose diacetate (A) existing in the acrylonitrilebased polymer (B), and a size and a number of the recess parts in thesurface of the composite fiber can be controlled.

For Example 4 and Comparative examples 1, 3 and 5 in Table 1, evaluationwas executed for the fibers obtained in the same conditions as those ofanother examples and the comparative examples except that a hole shapeof the spinnelette was changed from a round type to an elliptical typeto prepare the fiber with a ratio of the longest diameter and theshortest diameter as shown in Table 1.

In the case of Comparative example 4 with the (A)/(B) solid componentratio of 50/50, the fiber cannot be obtained stably because filamentbreaks were generated frequently at the spinning process. Therefore,execution of the evaluation thereof was impossible as well.

As it is understood from Table 1, even in the case where the ratio ofthe longest diameter and the shortest diameter of the composite fiber is2, if the number of the recess parts appearing on the fiber surface is 4or less, a dry feeling is poor, and deodorizing performance with respectto the isovaleric acid and the acetic acid is low.

Moreover, as to a feeling evaluation for a commercially availablecellulose diacetate 100% fiber as Comparative example 5 (produced byMitsubishi Rayon Corp. “Linda” 3.3 dTex), although the dry feeling andthe tense feeling were equivalent to those of the acrylic basedcomposite fiber of the invention, the soft feeling was poor comparedwith the acrylic based composite fiber of the invention.

Process Ability of Yarn Spinning of Examples 1, 3, 5 and ComparativeExample 6

Next, for the composite fibers of the above-mentioned Examples 1, 3, and5 and Comparative example 6, strength, dry elongation, knot strength,knot elongation and process ability of yarn spinning of each singlefiber were evaluated. Results are shown in Table 3. Here, the compositefiber of Comparative example 6 was produced in the same conditions asthe Comparative example 4 except that the drawing ratio was changed to 3times.

As to the evaluation of the process ability of yarn spinning, spun yarnof a 2/32 yarn number count were produced by cutting the compositefibers of Example 1, 3, and 5 and the new comparative example 6 havingthe different (A)/(B) solid component ratios to 51 mm, and mixing withan ordinary acrylic fiber of 2.2 dTex and a 51 mm fiber length at 30/70mixing ratio.

TABLE 3 Solid com- ponent Process mixing Single Dry Knot ability ofratio of fiber elon- Knot elon- yarn A/B strength gation strength gationSpinning Example 1 10/90 2.3 41.5 2.2 41.0 Good Example 3 30/70 2.2 41.02.0 38.0 Good Example 5 40/60 1.9 32.5 1.8 31.0 Good Comparative 50/501.3 26.0 1.4 24.5 Poor example 6

As it is apparent from Table 3, there is no problem in the processability of yarn spinning for Examples 1 and 3. As to the process abilityof yarn spinning with the (A)/(B) solid component ratio of 40/60(Example 5), although fly is generated slightly, it was at a levelsubstantially without a problem. In contrast, in the case of Comparativeexample 6 with the (A)/(B) solid component ratio of 50/50, thespinability is poor (for example the filament breaks were generatedfrequently at the spinning process). Moreover, the process ability ofyarn spinning was poor. (Fly is generated.)

From this, it was learned that the process ability of yarn spinningequal to that of an ordinary acrylic fiber spinning process can beobtained as long as the single fiber strength of the above-mentionedcomposite fiber is 1.8 CN/dTex or more, the dry elongation is 30% ormore, the knot strength is 1.8 CN/dTex or more and the knot elongationis 30% or more. In the case where these values are not satisfied as inthe case of the composite fiber of Comparative example 6, the processability of yarn spinning becomes poor.

“Deodorizing Property of Each Kind of Spun Yarn with Respect to anAcetic Acid, an Ammonia and a Nonenal”

Knitted fabric of a plain stitch organization was knitted after cuttingthe composite fiber obtained in Example 3 (single fiber fineness 2.2dTex), the acrylic fiber (single fiber fineness 2.2 dTex), rayon (singlefiber fineness 1.3 dTex), and ram wool (64S) each by 51 mm, and mixingby the mixing ratio shown in Table 4, and producing spun yarns of a 1/52yarn number. On the other hand, a dyeing liquid was prepared by adding0.25 g of a dye (Hodoya Kagaku Corp., Kachiron Blue KGLH), 1 g of anacetic acid, and 0.25 g of a sodium acetate to 1,000 g of pure water.The dyeing liquid was heated to 100° C. 50 g of the above-mentionedknitted fabric was soaked in the dyeing liquid and maintained at 100° C.for 30 minutes. After that, the dyed fabric was washed with water,dehydrated and dried, and a cation dyeing was executed. The deodorizingproperty of these fabrics with respect to an acetic acid and ammoniawere evaluated. Results are shown in Table 4. The deodorizing propertyof the knitted fabrics of Example 6 and Comparative example 7 withrespect to a nonenal was evaluated. The deodorizing ratios were 90% and38% respectively.

TABLE 4 Mixing ratio Fiber Deodorizing obtained ratio (%) in AcrylicAcetic Example 3 fiber Rayon Wool acid Ammonia Comparative 0 100 0 0 5454 example 7 Example 6 30 70 0 0 95 79 Example 7 30 40 30 0 97 94Example 8 30 40 0 30 96 97

As it is apparent from Table 4, the deodorizing property of the knittedfabric made of an ordinary acrylic fiber (Comparative example 7) was notat all satisfactory. In contrast, in the case that the mixed knittedfabric of the composite fiber of Example 3 and the acrylic fiber,although the deodorizing property of the fabric has slightly lowevaluation in the deodorizing property with respect to the ammonia, itis no problem in a practical use. Besides, since it has high deodorizingproperty evaluation with respect to the acetic acid, it is easilyunderstandable that the composite fiber of the invention has theexcellent deodorizing property as well.

“Moisture Absorbing and Retaining Property of Each Kind of Spun Yarn”

Knitted fabric of a plain stitch organization was knitted after cuttingthe composite fiber obtained in Example 3 (single fiber fineness 2.2dTex) and the acrylic fiber (single fiber fineness 2.2 dTex) each by 51mm, and mixing them by a 50/50 mixing ratio, and producing spun yarns ofa 1/52 yarn number. Thereafter, a knitted fabric with theabove-mentioned cation dyeing was obtained (Example 9). After leavingthe knitted fabric and a knitted fabric made of an ordinary acrylicfiber (Comparative example 7) in a 20° C. temperature and 65% RHhumidity environment for 4 hours, they were left in a 40° C. temperatureand 90% Rh humidity environment for 24 hours and successively left in a20° C. temperature and 65% RH humidity environment for 24 hours, then,the moisture absorbing and retaining property of each knitted fabric wasevaluated. Results are shown in FIG. 3.

Example 9 was superior to the acrylic fiber knitted fabric (Comparativeexample 7), and it has a sufficient moisture absorbing and retainingproperty in the different environment conditions. The moisture absorbingproperty was evaluated for a mixed spun yarn of a tow of the cellulosediacetate (single fiber fineness 2.2 dTex) and a tow of the acrylicfiber (single fiber fineness 2.2 dTex) at 15/85 ratio, paralleled by asliver after leaving it in a 20° C. temperature and 65% RH humidityenvironment for 24 hours. The moisture absorbing property was 1.8%,which is poorer than that of Example 9.

Moisture Absorbing Property of Examples 10 to 11 and ComparativeExamples 8 to 10

To prepare samples of Examples 10 and 11, the fibers obtained inExamples 3 and 4 were treated with different concentration of NaOHrespectively for 30 minutes at 60° C. In the case of Comparativeexamples 8 and 9, the fiber obtained in Comparative example 1 wastreated with different concentration of NaOH for 30 minutes at 60°. Inthe case of Comparative example 10, the fiber obtained in Comparativeexample 2 was treated with NaOH which using amount is 12wt % per fiberweight under the same temperature. Evaluation on the moisture absorbingproperty, the weight reduction ratio of the obtained fibers is shown inTable 5. In the acrylic based composite fibers of Examples 10 and 11,the cellulose acetate, the cellulose and the acrylic based polymer werepresent. Although the cellulose acetate, the cellulose and theacrylonitrile based polymer were similarly present in the acrylic basedcomposite fiber in Comparative example 10, satisfactory performance wasnot obtained because the cellulose diacetate is 5%.

Moisture Absorbing Property of Example 12

To prepare the sample of Example 12, the fiber obtained in Examples 5was treated with NaOH of which using amount is 14wt % per fiber weightfor 30 minutes at 80° C. The cellulose acetate was changed to be thecellulose by an alkaline process so that the cellulose and theacrylonitrile based polymer were present in the acrylic based compositefiber. Evaluation on the moisture absorbing property and the weightreduction ratio of the obtained fiber is shown in Table 5.

TABLE 5 Solid Using amount of Cellulose Specimen No. component NaOH (%with Moisture Moisture acetate weight supplied for mixing ratio respectto absorbing absorbing reduction NaOH use of A/B fiber weight) ratio Aa(%) ratio Ab (%) ΔA ratio (%) Example 10 Example 3 30/70 12 8.1 6.8 1.230 Example 11 Example 3 30/70 3 4.8 3.2 1.2 11 Example 12 Example 540/60 14 13.0 11.6 1.4 40 Comparative Comparative  0/100 3 1.5 1.2 0.3 0example 8 example 1 Comparative Comparative  0/100 0 1.5 1.2 0.3 0example 9 example 1 Comparative Comparative  5/95 12 2.5 1.8 0.7 30example 10 example 2

1. An acrylic based composite fiber comprising 10 to 40% by weight of atleast one of cellulose acetate or cellulose and 60 to 90% by weight ofan acrylonitrile based polymer, said acrylic based composite fiberhaving a structure wherein at least one of the cellulose acetate orcellulose is present as an island component in a cross sectionperpendicular to a fiber axis, and the acrylonitrile based polymer ispresent as a sea component, and single fiber strength is 1.8 CN/dTex ormore, dry elongation is 30% or more, knot strength is 1.8 CN/dTex ormore, and knot elongation is 30% or more.
 2. The acrylic based compositefiber according to claim 1, having a structure wherein at least one ofthe cellulose acetate or cellulose is present as the island componentand contacts another island component in a cross section along the fiberaxis direction.
 3. The acrylic based composite fiber according to claim1, wherein a vacant hole is present inside the fiber.
 4. The acrylicbased composite fiber according to claim 1, wherein a ratio of thelongest diameter and the shortest diameter of a fiber cross section is 2or less, and 5 or more recess parts of from 0.3 μm to 3 μm width andfrom 0.3 μm to 3 μm depth are present in a fiber cross section outercircumferential part.
 5. The acrylic based composite fiber according toclaim 1, having a deodorizing ratio with respect to a carboxylic acid of90% or more.
 6. The acrylic based composite fiber according to claim 1,having a deodorizing ratio with respect to an acetic acid of 95% ormore.
 7. The acrylic based composite fiber according to claim 1, havinga deodorizing ratio with respect to a nonanal of 90% or more.
 8. Theacrylic based composite fiber according to claim 1, having a moistureabsorbing ratio Aa at a 40° C. temperature and 90% RH humidityenvironment of 15.0% or less, a moisture absorbing ratio Ab at a 20° C.temperature and 65% RH humidity environment of more than 2%, and amoisture absorbing ratio difference ΔA (=Aa−Ab) at the time of transferfrom the 40° C. temperature and 90% RH humidity environment to the 20°C. temperature and 65% RH humidity environment of less than 1.5.
 9. Theacrylic based composite fiber according to claim 8, wherein the moistureabsorbing ratio Aa at the 40° C. temperature and 90% RH humidityenvironment is from 3.0% to 8.0%, and the moisture absorbing ratio Ab atthe 20° C. temperature and 65% RH humidity environment is more than 2%and less than 6.5%.
 10. A fiber composite comprising the acrylic basedcomposite fiber according to claim
 1. 11. The acrylic based compositefiber according to claim 2, wherein a vacant hole is present inside thefiber.
 12. The acrylic based composite fiber according to claim 2,wherein a ratio of the longest diameter and the shortest diameter of afiber cross section is 2 or less, and 5 or more recess parts of from 0.3μm to 3 μm width from 0.3 μm to 3 μm depth are present in a fiber crosssection outer circumferential part.
 13. The acrylic based compositefiber according to claim 2, having a deodorizing ratio with respect to acarboxylic acid of 90% or more.
 14. The acrylic based composite fiberaccording to claim 2, having a deodorizing ratio with respect to anacetic acid of 95% or more.
 15. The acrylic based composite fiberaccording to claim 2, having a deodorizing ratio with respect to anonanal of 90% or more.
 16. The acrylic based composite fiber accordingto claim 2, having a moisture absorbing ratio Aa at a 40° C. temperatureand 90% RH humidity environment of 15.0% or less, a moisture absorbingratio Ab at a 20° C. temperature and 65% RH humidity environment of morethan 2%, and a moisture absorbing ratio difference ΔA (=Aa−Ab) at thetime of transfer from the 40° C. temperature and 90% RH humidityenvironment to the 20° C. temperature and 65% RH humidity environment ofless than 1.5.
 17. The acrylic based composite fiber according to claim16, wherein the moisture absorbing ratio Aa at the 40° C. temperatureand 90% RH humidity environment is from 3.0% to 8.0%, and the moistureabsorbing ratio Ab at the 20° C. temperature and 65% RH humidityenvironment is more than 2% and less than 6.5%.
 18. A fiber compositecomprising the acrylic based composite fiber according to claim 2.